Activation of Kagome lattice-structured Cu3V2O7(OH)2·2H2O volborthite via hydrothermal crystallization for boosting visible light-driven water oxidation.

We report a feasible strategy via hydrothermal crystallization to activate Kagome lattice-structured Cu3V2O7(OH)2·2H2O volborthite mineral as a stable visible-light-driven photocatalyst. It was demonstrated to play a crucial role in stimulating absorption ability and photodegradation performance for the removal of methylene blue present in high concentration. In contrast, direct calcination was almost ineffective, whereas post-calcination was significantly detrimental. Moreover, the photocatalytic water oxidation activity of hydrothermally crystallizated volborthite was comparable to that of BiVO4, and it was clearly higher than those of WO3 and g-C3N4 from aqueous NaIO3 solution. By further in situ decoration with an optimum amount of CoOx cocatalysts (i.e., 2 wt%), the oxygen evolution rate of volborthite was greatly enhanced, and it was 1.6-fold, 1.8-fold and 2.9-fold higher than those of BiVO4, WO3 and g-C3N4, respectively. The importance of hydrothermal crystallization can be elucidated in terms of water-Kagome lattice structure interactions involving built-in intrinsic electric field and formation of single hydrogen bonds.

New Understanding on Photocatalytic Mechanism of Nitrogen-Doped Graphene Quantum Dots-Decorated BiVO4 Nanojunction Photocatalysts.

Bismuth vanadate (BiVO4) is a promising candidate as a visible-light-driven photocatalyst in the aspect of practical applications. To investigate the origin of active species from BiVO4 and understand the influence of the variations of the photocatalytic process, comparative studies on zero-dimensional nitrogen-doped graphene quantum dot (NGQD)-decorated BiVO4 have been carried out for methylene blue photodegradation. It was found that the hydroxyl group-rich NGQD surface and the established heterojunction structure between NGQDs and BiVO4 were greatly beneficial for the conversion of the •OH radical. With NGQD decoration, the dominant oxidant species for NGQDs/BiVO4 were confirmed to be •OH and H2O2, rather than holes originating from the valence band of unmodified BiVO4. The synergistic photocatalytic mechanism with respect to the interfacial charge transport and the conversion of active species was proposed. The achievement of the controllable active species significantly altering the activity may be applied for different photocatalytic reactions.

Controllable Growth of Ultrathin P-doped ZnO Nanosheets.

Ultrathin phosphor (P)-doped ZnO nanosheets with branched nanowires were controllably synthesized, and the effects of oxygen and phosphor doping on the structural and optical properties were systematically studied. The grown ZnO nanosheet exhibits an ultrathin nanoribbon backbone with one-side-aligned nanoteeth. For the growth of ultrathin ZnO nanosheets, both oxygen flow rate and P doping are essential, by which the morphologies and microstructures can be finely tuned. P doping induces strain relaxation to change the growth direction of ZnO nanoribbons, and oxygen flow rate promotes the high supersaturation degree to facilitate the growth of nanoteeth and widens the nanoribbons. The growth of P-doped ZnO in this work provides a new progress towards the rational control of the morphologies for ZnO nanostructures.